Troubles with HASH MD5 of large XML files

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I am having troubles when trying to calculate the hash MSD5 of an XML file. I have a third party validator that calculates it correctly, i am trying to make my own validator in c# but it does not work, i keep getting an invalid hash MD5 with big xml files, with small files it works fine. The big file has around 63000 lines.

The code in C#:

C#

public string GenerateHash(string xml, string hashOrigin = null)
    {

        XDocument doc = XDocument.Parse(xml);

        StringBuilder sb = new StringBuilder();

        string pKeyEncode = doc.Root.Value;
        if (!string.IsNullOrEmpty(hashOrigin))
            pKeyEncode = pKeyEncode.Replace(hashOrigin, "");

        MD5CryptoServiceProvider _cs = new MD5CryptoServiceProvider();
        byte[] _bs = Encoding.GetEncoding("ISO-8859-1").GetBytes(pKeyEncode);
        _bs = _cs.ComputeHash(_bs);
        StringBuilder _s = new System.Text.StringBuilder();
        foreach (byte _b in _bs)
        {
            _s.Append(_b.ToString("x2").ToLower());
        }
        int a = _s.GetHashCode();
        return _s.ToString();
    }

Posted 21-May-15 9:43am

Member 11709458

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Sergey Alexandrovich Kryukov · Answer 1 · 2015-05-21T10:37:00

You are doing it wrong.

If you really have XML file, read the file as is, into array of bytes, not string. It will make your code independent on encoding.
To compute MD5 has, uses the class System.Security.Cryptography.MD5. Yes, it is abstract, but you need to get the provider instance via its factory method Create, as shown in the code sample at the end:
https://msdn.microsoft.com/en-us/library/system.security.cryptography.md5%28v=vs.110%29.aspx[^].

For the creation of MD5 class instance, please see the method Program.Main.

—SA